Rob wrote: > David Lord <[email protected]> wrote: >> David Lord wrote: >>> David J Taylor wrote: >>>> OT: GPS18x LVC failure >>>> >>>> My GPS18x LVC stopped working a couple of days ago. There appears to >>>> +5V going into the unit, and the serial output is stuck around -5V >>>> with no signs of data on the 'scope. Garmin have accepted the unit >> I'm guessing you hit (-) rather than (+), otherwise something >> odd as with my unit the supplies are +5V and 0V, output spec >> is 0V to +5V. Where was the -5V generated? If the -5V was real >> then it would indicate some sort of internal fault. > > No, it is normal for an RS232 output to output positive and negative > voltages. > > Where was the -5V generated? Internal to the device. Using a DC-to-DC > convertor, often a charge pump using some diodes and capacitors. > > This is not a fault.
I know what full rs232 is, but specs for the 18x-LVC I have are 0V to +5V and do not mention any negative swing. At a guess my 18x-LVC does not output < 0V. I'll measure when I next connect up but it does not work well or at all with usb-serial converters I've tried. With Conrad module I fudged the supplies to give a -Ve output swing and that did start giving some usable output via usb-serial. David (Mr rs232 when I was at uni) _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
